In recent decades, more than 100 different mechanophores with a broad range of activation forces have been developed. For various applications of mechanophores in polymer materials, it is crucial to selectively activate the mechanophores with high efficiency, avoiding nonspecific bond scission of the material. In this study, we embedded cyclobutane-based mechanophore cross-linkers (I and II) with varied activation forces (fa) in the first network of the double network hydrogels and quantitively investigated the activation selectivity and efficiency of these mechanophores. Our findings revealed that cross-linker I, with a lower activation force relative to the bonds in the polymer main chain (fa-I/fa-chain = 0.8 nN/3.4 nN), achieved efficient activation with 100% selectivity. Conversely, an increase of the activation force of mechanophore II (fa-II/fa-chain = 2.5 nN/3.4 nN) led to a significant decrease of its activation efficiency, accompanied by a substantial number of nonspecific bond scission events. Furthermore, with the coexistence of two cross-linkers, significantly different activation forces resulted in the almost complete suppression of the higher-force one (i.e., I and III, fa-I/fa-III = 0.8 nN/3.4 nN), while similar activation forces led to simultaneous activations with moderate efficiencies (i.e., I and IV, fa-I/fa-IV = 0.8 nN/1.6 nN). These findings provide insights into the prevention of nonspecific bond rupture during mechanophore activation and enhance our understanding of the damage mechanism within polymer networks when using mechanophores as detectors. Besides, it establishes a principle for combining different mechanophores to design multiple mechanoresponsive functional materials.
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This content will become publicly available on November 11, 2025
Mechanochemistry of cyclobutanes
The field of polymer mechanochemistry has been revolutionized by implementing force-responsive functional groups—mechanophores. The rational design of mechanophores enables the controlled use of force to achieve constructive molecular reactivity and material responses. While a variety of mechanophores have been developed, this Mini Review focuses on cyclobutane, which has brought valuable insights into molecular reactivity and dynamics as well as innovations in materials. We discuss its reactivity and mechanism, dynamics and stereoselectivity, as well as impacts on material properties.
more » « less- Award ID(s):
- 2204079
- PAR ID:
- 10552023
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- Science China Chemistry
- ISSN:
- 1674-7291
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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